Fuel tanks such as used for heating oil have a somewhat limited life because of water condensation within the tank rusting or corroding the tank wall to destroy the integrity thereof. This typically occurs in summer conditions where a fuel tank may be empty for several months and the condensed water collects at the bottom of the tank to rust a hole in the tank bottom. The bottom of the tank is also vulnerable to failure because it must withstand the greatest fluid pressure when the tank is full.
Since the greatest stress occurs at the bottom of a fuel oil tank, the life of the tank would be increased if after some period of time, somewhat less than the usual expected life of the tank, the tank could be actually inverted and set up for operation in this inverted condition.